Classification



Jan. 11,1938. 5, PELLETT 2,105,126

CLASSIFICATION Filed April 1, 1936 3 Sheets-Sheet l I a I L H 39 m J8 46 v ET:

fazi f INVENTOR 1/226115'092 J'J eZ/df BY 7 2%, 7% M ATTORNEYS Jan. 11, 1938. J. 5. PELLETT 2,105,126

CLASSIFICATION Filed April 1, 1956 3 Sheets-Sheet 2 If \NVENTOR f6 Z/ I Jim/{1502? JPZ/efi 7W; QM, Wm WM- ATTORNEYS Patented Jan. 11, 1938 PATENT OFFICE CLASSIFICATION Jackson S. Peliett, Franklin, N. J., assignor to e New Jersey Zinc Company,

New York,

N. Y., a corporation of New Jersey Application April 1, 1936, Serial No. 72,014

20 Claims.

comminuted mineral: particles by hindered settling andhas for is object the provision of certain improvements in the method of and apparatus for hindered settling classification.

In hindered settling classification, a pulp of comminuted mineral particles in suspension in water is passed over a chamber or series of chambers provided with a constant stream or streams of rising water against which the mineral particles settle in a crowded but mobile condition, the chambers being provided with spigots or the like for discharging the classified product. The invention contemplates an improved method of and apparatus for controlling the discharge of the classified pulp (i. e., pulp which has been sub- -jected to classification in the chamber) inresponse to changes in the density of the pulp undergoing hindered settling. Thus, in accordance with one aspect of the invention, the discharge of classified pulp from the classifying chamber is automatically increased "or decreased as the density of the pulp undergoing-hindered settling increases or decreases. In the preferred form of the invention, the contemplated control of the classified pulp is effected by discharging the classified pulp into a control zoneor reservoir in. which a hydrostatic pressure is maintained, and then varying, preferably automatically, the hydrostatic pressure in the control zone in response to changes in the density of the pulp undergoing hindered settling. These and other novel features of the invention will be better understood from the following description taken in conjunctionwith the accompanying drawings, in which. s

Fig. 1- is a diagrammatic sectional elevation of a hindered settling classifier embodying the invention,

Figs. 2, 3, 4 and 5 are detail sectional elevations illustrating various devices for supplying rising streams of water to the classifying chamber in accordance with one of the novel aspects of the invention,

Figs. 6, 7 and 8 are diagrammatic sectional elevations of hindered settling classifiers embodying modified forms of the invention, and

Figs. 9, 10, 11 and 12 are detail views of a modified discharge for the classified pulpyFigs. 11 and 12 being sections on the section line 9-.9 of Fig. 9.

Referring to Figs. 1 and 2 of the drawings, the classifying chamber or pocket l5 has a hydraulic compartment "5 at its base and the customary. flared upper portion (Cl. 209-158) This invention relates to the classification of propriate head of water (indicated by x) is maintained in the pipe H by supplying water thereto at a. constant rate through a valved outlet l8 of a water tank [9 having an overflow 20 to maintain a constant level of water in the tank. The top of the hydraulic compartment I 6 is provided with a plurality of nozzles 2| for introducing streams of water into the bottom of the classifying chamber I5. The nozzles 2| are covered by caps 22 which may be attached to the roof or cover of the compartment by brackets 23 (Fig. 2). The compartment I6 has a drain pipe 24 in its bottom. In practice, the classifier generally comprises a series of adjacent classifying chambers over which the pulp to be classified progressively passes. In such a classifier, the diameters of the pipes ll progressively decrease from the feed end of the classifier, at which coarse material is-treated, to the discharge end, at which fine material is treated; that is to say, the water supply pipe II for the first chamber of the classifier feed end) will be larger than the water supply pipe II for the second chamber, and the water supply pipe for the second chamber will be larger than V that .for the third chamber, and so on. The widened or flared portions I 5 of the series of chambers guide the discharge-of water and fines to an appropriate launder at the discharge end of a spigot -2i: for the discharge. of classified pulp into a control reservoir 26. The flow of pulp through the spigot 25- is determined by the difference between the hydrostatic pressure prevailing in the reservoir and the hydrostatic pressure due v to the pulp'in the classifying chamber IS. The hydrostatic pressure in'the reservoir 26 results from the head of water (indicated by Z) in a pipe 21 for supplying water to the; reservoir. Perforated baffles 28 and 29 are provided near the top and bottom, respectively, of the reservoir for distributing the flow of water through the reservoir to the discharge outlet '30, and thereby preventing the development of a vortex that might withdraw pulp through the spigot 25 by suction. The top of the control reservoir has a bleeder nozzle 3|, equipped with a valve, for permitting the esstand pipe 32 extends downwardly into the chamber I 5 to approximately the level of the spigot 25. At its upper end the stand pipe 32 terminates in a float chamber 33. The stand pipe is filled with clear water, and the apparatus is so adjusted that when the classifier is in normal operation the level of water in the stand pipe extends up into the float chamber. Since the density of the pulp in the classifying chamber I5 is greater than the density of water, the level of the water (y) in the float chamber 33 will be substantially above the level of the pulp in the chamber l5.

A float 34 is supported by the water in the fioat chamber 33. The float 34 is connected by a chain 35, or the like, with a horizontally disposed lever 36 by means of a screw 31 permitting adjustment in the length of the chain 35. The lever is pivoted at 38 and counter-poised by a weight 39. A link 40 connects the lever with a valve 4| at the upper end of the pipe 21 which extends into a water tank 42 having an overflow 43 for maintaining a constant level of water in the tank. Vertical movement of the link 40 actuates the valve 4| to open and close communication of the pipe 21 with the water in the tank 42. A water main 46 supplies Water to the tanks |9 and 42 through valve-controlled, outlets 41 and 48, respectively.

The apparatus is so adjusted that when the float 34 ascends in the float chamber 33 on ac-' count of an increase in pulp density in the classifying chamber |5, the link 40 closes the valve 4| so as to cut off the supply of water from the tank 42 to the pipe 21. In consequence, the escape of water from the outlet 30 at the base of the control reservoir 26 causes the water level (2:) in the pipe 21 to descend'with a resulting decrease in the hydrostatic pressure in the control reservoir. In consequence, the resistance of the control reservoir to the outflow of pulp through the spigot 25 is diminished, and therefore the discharge of pulp through the spigot is accelerated, and the density of the pulp in the classifying chamber I5 is decreased. The link 40 is provided with a counterweight 44 to decrease its backlash, and insure prompt closure of the valve 4| when the float 34 rises. In order to provide a minimum head of water in the pipev 21, the upper portion of the pipe within the tank 42 is provided with a bleeder inlet 45 through which a properly adjusted minimum supply of water flows into the pipe 21,from the tank 42 even when the valve 4| is closed. This insures the maintenance of a minimum fiow of water to the control reservoir 26 necessary to maintain suflicient pulp fluidity for discharge flow. The spigot 25 is designed with a steeply sloping upper portion and a vertical lower portion in order to prevent the escape of pulp on the lower side of the sloping spigot accompanied by the inflow of water in the upper sloping portion.

When the float 34 descends in the float chamber 33 on account of a decrease in pulp density in the classifyingchamber l5, the link 40 opens the valve 4| so as to permit the supply of water from the tank 42 to the pipe 21. In consequence, the hydrostatic resistance of the control reservoir 26 to the outflow of pulp through the spigot 25 is increased, and therefore the discharge of pulp through the spigot is diminished, and the density of the pulp in the classifying chamber |5 is increased. I

The automatic control of the discharge of classified pulp in response to changes in the density of the pulp undergoing classification tends to maintain a substantially constant pulp density in the classifying chamber. Uniformity of operation of the classifier is further facilitated and brought about by maintaining .the velocity of the upward current of water substantially constant. The upflow of water through the classifying chamber I5 is determined by the head (:0) of water in the supply pipe l1. Water is supplied at a constant rate to the pipe |1 as hereinbefore explained. An increase in density of the pulp in the classifying chamber increases the resistance to the ascending current of water. 7

This increased resistance causes the head of water (as) in the pipe H to rise with resulting increase in the hydrostatic pressure driving the current of water upwards, whereby the water current is maintained at a substantially constant rate even when the resistance of the pulp in the classifying chamber increases on account of increasing density.

The invention further contemplates an improved method of supplying a uniform ascending stream of water to the classifying chamber. As illustrated in Figs. 1 and 2, the restricted openings or nozzles 2| are provided with caps 22 to prevent clogging with settled solid particles whenever the rising water supply may be shut off. These caps 22, by deflecting the incoming water, provide initially an approximately uniform distribution of the rising water over the cross section of the chamber. The spigot 25 is positioned a substantial distance above the nozzles 2|, so that the ascending current of water has time to become uniformly distributed and eddies in it are destroyed before the water has passed into the effective classifying zone of the chamber above the spigot. Furthermore, the position of the spigot 25 a substantial distance above the nozzles 2| permits the accumulation or building up of a substantial body of suspended comminuted particles below the spigot, which particles act to secure a substantially uniform rising current of liquid throughout the cross-section of the chamber at the level of the discharge for classified pulp- In Figs. 3 and 4 of the drawings a pair of water supply pipes I1 extend laterally into the bottom of the classifying chamber I5 and each is provided with a plurality of upwardly directed nozzles 2| covered by a common cap 22'. In Fig. 5, the nozzles 2| are covered with a rubber cap 22" having a slot in the top thereof which automatically closes when the pressure and flow of the ascending water ceases.

Fig. 6 of the drawings illustrates the embodiment of the invention in a classifier provided with more conventional pulp discharge means. The

pipe l1 supplies water to a hydraulic compartment 49, having a perforated roof or cover through which the water rises into the classifying chamber 5|. Pulp is discharged from the chamber 5| through the spigot 52 into the control reservoir 53 having a discharge outlet 54. The water supply pipe 21 communicates with the reservoir 53, and the discharge of classified pulp from'the chamber 5| is controlled by the hydrostatic pressure in the reservoir 53 in the same manner as in the classifier of Fig. 1, the same reference characters designating corresponding elements in the two figures.

Figs. 7 and 8 illustrate modifications of the invention in which irregularities in the density of the pulp feed to the classifier are prevented from affecting the rate of discharge of classified pulp through the spigot 25.

Referring first to Fig. 7, two stand pipes 55 and 56 extend downwardly into the classifying chamber I 2,105,i2e to diflerent levels (a and b respectively). The

pipes 55 and 56 terminate at their upper ends in separate float chambers respectively, are connected by links BI and 62,

respectively, to the extremities of a centrally 50 do not change their positions, being held motionless by the lever 53. Consequently, a uniform ascent of water in the stand pipes 55 and 55does not move the lever 36 (Fig. 1) and hence does not afiect the valve 4! regulating the supply of water to the end of the pipe 21. Since any increase in pulp density above the level of the higher water inlet b of the stand pipe 56 must cause water to-ascend as ,far in float chamber 58 as in float chamber 59, such an increase in pulp density does not afiect the discharge of classified pulp through'the spigot 25. However, any increase in pulp density below the level I) will cause water to rise to a disproportionately greater level in float chamber 5]. -In consequence, float 59 will be forced upwardly, and valve ti (Fig. 1) will thereby be closed. The closing of valve ti will permit the water level (a) in pipe 21 to fall, with resulting decrease of hydrostatic pressure in the control reservoir 25 and resulting increase in discharge rate through spigot 25.

It will be noted that the inlet level of the stand pipe 55 is at approximately the level of the spigot 25, so that the discharge of classified pulp from the chamber is controlled by the density of the pulp from the level of the spigot 25 up to the level (b) of the inlet of the stand pipe 55. In the classifier of Fig. 7, the water inlet nozzles 21 of the hydraulic compartment 15 are covered with the slotted rubber caps 22" (Fig. 5).

In Fig. 8 of the drawings, the stand pipes 55 and 5B communicate withtthe compartments 5t and 65 of a diiierential pressure regulator 5'5. The two compartments are separated by a diaphragm 51 to which the chain 55 is connected.

The pressure regulator functions in an equivalent manner to the lever 53 of Fig. 7, and the apparatus operates in substantially the same manner as explained in connetion with the classifier of that figure.

In Fig. 9 of the drawings, the spigot 25 of Fig. 1 is replaced by a rubber flutter valve 53. The classifying chamber l5 has an opening 55 for the discharge of classified pulp. The rubber flutter valve 58 is secured in position over the opening '59 by a frame ill on the control reservoir side of the opening. Fig. 11 illustrates the flutter valve closed by the hydrostatic pressure in the reservoir 25, and Fig. 12 illustrates the flutter valve open by a decrease in the hydrostatic pressure in the reservoir to permit the discharge of classified pulp.

The invention is particularly applicable to the classification of minerals preparatory to a concentration operation, such as by Wilfiey Tables and the like. However, the invention may be applied witth advantage to the classification of any comminuted solid material and in the appended claims I have used the word mineral in a generic sense to include any solid material susceptible to classification by hindered settling. As is well understood in the art, other liquid mediums may in certain cases be substituted for water without departing from the spirit of the invention.

51 and 58, respectively. Floats 59 and 60 in the float chambers 51 and 58,

I claim:

1. In a. hindered settling classifier, a chamber in which mineral particles are permitted to settle against a rising current of water and provided with a free discharge for classified pulp, means for maintaining\a substantially constant rising current in the chamber, a control reservoir communicating with said classified pulp discharge, means for establishing a hydrostatic pressure in said reservoir to oppose discharge of the classified pulp, and means for varying inversely the hydrostatic pressure in said reservoir in response to changes in pulp density within the chamber while maintaining a substantially constant rising current through said chamber.

2. In a hindered settling classifier,a chamber in v which mineral particles are permitted to settle against a rising current of water and provided with a discharge for classified pulp, means for maintaining a substantially constant rising current in the chamber, a control reservoir communicating with said classified pulp discharge, means for establishing a hydrostatic pressure in said reservoir, and means for automatically decreasing the hydrostatic pressure in said reservoir upon an increase in the density of the pulp within said chamber and for increasing the hydrostatic pressure in the reservoir upon a decrease in the density of the pulp within the chamber while maintaining a substantially constant rising current through said chamber. a

3. In a hindred settling classifier, a chamber in which mineral particles are permitted to settle against a rising current of water and provided with a discharge for classified pulp, means for maintaining a substantially constant rising current in the chamber, a control reservoir communicating with said classified pulp discharge, means for establishing a hydrostatic pressure in said reservoir, means responsive to changes in the density of the pulp within said chamber, and means for causing said pulp density responsive means to decrease the hydrostatic pressure in said reservoir upon an increase in the density of the pulp within said chamber and to increase thehydrostatic pressure in the reservoir upon a decrease in the density of the pulp within the chamber while maintaining a substantially constant rising current through said chamber.

4. In a hindered settling classifier, a chamber in which mineral particles are permitted to settle against a rising current of water and provided with a discharge for classified pulp, means for setting up a hydrostatic pressure to oppose the discharge of classified pulp from the chamber and means for varying the hydrostatic pressure opposing the discharge inversely in response to changes in pulp density within a predetermined height above the level of said discharge and independent of irregularities in the density of the pulp fed to the classifier.

5. In a hindered settling classifier, a chammr in which mineral particles are permitted to settle against a rising current of water and provided with a discharge for classified pulp, a control reservoir communicating with said classified pulp discharge, means for establishing a hydrostatic pressure in said reservoir, and means for automatically decreasing the hydrostatic pressure in said reservoir upon an increase in the density of the reservoir upon a decrease in the density of the pulp within said predetermined portion of the pulp column.

6. In a hindered settling classifier, a chamber in which mineral particles are permitted to settle against a rising current of water, means for introducing streams of water into the bottom of said chamber, means cooperating with the entering streams of water for preventing the interference of mineral particles therewith, and means for the discharge from said chamber of classified pulp positioned above the entering streams of water a distance sufficient to permit the substantially uniform upward flow of water throughout a horizontal section of the chamber at the level of the discharge means.

'7. In a hindered settling classifier, a chamber in which mineral particles are permitted to settle against a rising current of water, means for introducing streams of water into the bottom of said chamber, means positioned in the path of said entering streams of water for deflecting the water and for holding mineral particles away from the entering streams of water, and means for the discharge from said chamber of classified pulp positioned above the entering streams of water a distance such that the entering streams of water attain a substantially uniform velocity throughout a horizontal section of the chamber at the level of the means for the discharge of classified pulp.

8. In a hindered settling classifier, a chamber in which mineral particles are permitted to settle against arising current of water, means for introducing streams of water into the bottom of said chamber, means cooperating with the entering streams of water for preventing the interference of mineral particles therewith, means for the discharge from said chamber of classified pulp positioned a substantial distance above the entering streams of water, said substantial distance being such that the rising current of water throughout the chamber at the level of the discharge means has substantially uniform velocity, and means for varying the discharge of classified pulp from the chamber in response to changesin pulp density within the chamber.

9. In a hindered settling classifier, a chamber in which mineral particles are permitted to settle against a rising current of water, means for introducing streams oi water into the bottom of said chamber from a supply having a hydrostatic head responsive to changes in the density of the pulp in said chamber, means for continuously furnishing water ata uniform rate to said supply, means cooperating with the entering streams of water for preventing the interference of mineral particles therewith, means for the discharge from said chamber of classified pulp positioned a substantial distance above the entering streams of water, said substantial distance being such that the entering streams of water produce a substantially constant rising current of water throughout the chamber at the level of the means for the discharge of classified pulp, and means for varying the discharge of classified pulp from the chamber in response to changes in pulp density within the chamber.

10. The improvement in the hydraulic classification of comminuted mineral particles by hindered settling in a classifier chamber in a rising current of liquid which comprises discharging the classified pulp into liquid in a control chamber communicating with the classifier chamber, and

varying the hydrostatic head on the liquid in the control chamber in inverse response to changes in the density of the pulp undergoing classification by changing the height of a column of liquid communicating with said control chamber, whereby the rate of discharge of classified pulp into the control chamber isvaried directly as its density.

11. In a hindered settling classifier, a classifier chamber in which mineral particles are permitted to settle against a rising current of water and provided with a discharge'for classified pulp at a.

lower portion thereof, a control chamber filled with a liquid under pressure and communicating with said discharge, a density-determining means disposed in said classifier chamber and responsive to variations in the density of pulp undergoin classification, and means for increasing and decreasing the pressure on the liquid in the control chamber in response respectively to decreases and increases determined by the density-determining means.

12. Apparatus according to claim 11 in which the density-determining means comprises a liquid-containing conduit projecting into and communicating with the classifier chamber and a float supported by the liquid in the conduit.

13. Apparatus according to claim 11 in which the density-determining means comprises a plurality of liquid-containing conduits projecting into and communicating with the classifier chamber at difierent levels and a plurality of lever-connected floats supported by the liquid in the respective conduits.

14. Apparatus according to claim 11 in which the density measuring meahs comprise's a conduit projecting into and communicating with the classifier chamber, said conduit being connected to a closed chamber having a flexible diaphragm that is movable by a change in pressure in the conduit.

15. The improvement in the hydraulic classification of comminuted mineral particles by hindered settling in a rising current of liquid in a chamber which comprises discharging classified pulp from said chamber into a body of liquid maintained under hydrostatic pressure and in contact with the liquid in the chamber, and varying the rate of 'discharge of the classified pulp in the chamber by automatically varying the hydrostatic pressure on the body of liquid in inverse response to changes in the density oi pulp undergoing classification in the chamber.

16. The improvement in the hydraulic classification of comminuted mineral particles by hindered settling against a current of liquid in a chamber which comprises discharging classified pulp from said chamber into a body of liquid maintained under hydrostatic pressure and in contact with the liquid in the chamber, and decreasing the hydrostatic pressure on the body of liquid upon an increase in the density of pulp undergoing classification in the chamber and increasing the hydrostatic pressure on the body of liquid upon a decrease in the density of pulp undergoing classification in the chamber.

17. The improvement in the hydraulic classification of comminuted particles by hindered settling in a rising current of liquid in a chamber which comprises discharging classified pulp from said chamber into a body of liquid maintained under hydrostatic pressure in contact with the liquid in the chamber, and while maintaining the rising current substantially constant automatically varying the resistance to discharge of the classified pulp by varying the hydrostatic pressure on the body of'liquid in inverse response to changes in the density of the pulp undergoing classification in the chamber.

18 In a hindered settling classifier, a chamber in which mineral particles are permitted to settle against a rising current of water and provided with an outlet for classified pulp, means for setting up a hydrostatic pressure to oppose discharge through said outlet from said chamber, and means for increasing said hydrostatic pres sure opposing the discharge upon a decrease in density of the pulp within the chamber and for decreasing said hydrostatic pressure upon an increase in density of the pulp within the chamber. 1

19. The improvement in the hydraulic classification of comminuted particles by hindered settling in a rising current of liquid in a chamber provided with a discharge for classified pulp which comprises setting up said rising current of liquid by introducing through an inlet a stream of liquid into the chamber at a substantial distance below the discharge for classified pulp, said distance being such as to permit the accumulation of a substantial body of suspended comminuted particles below said discharge and the attainment of a substantially uniform rising current of liquid throughout the cross-section of the chamber at the level of the discharge for classified pulp, and preventing said suspended comminuted particles from entering said inlet when the rising current of liquid is checked.

20. In a hindered settling classifier, a chamber in which mineral particles are permitted to settle against a rising current of liquid, an inlet for introducing a stream of'liquid into a lower portion of the chamber, a discharge for classified pulp from said chamber positioned above the entering stream of liquid a distance such that a body of suspended mineral particles accumulates in the chamber below the discharge and causes the entering stream to distribute itself with substantial uniformity through a cross-section of the chamber at the level of the discharge so that the rising current of liquid is substan-' tially uniform in the cross-section at said level, and means for preventing the entry of said suspended mineral particles into said inlet when the entering stream of liquid is checked.

JACKSON S. 

